Current sensor integrated circuits (ICs) are used in a wide variety of applications including motors, in which current through one or more motor windings is measured by measuring a voltage across a sense resistor coupled in series or “in-line” with the motor winding. Such current sensor ICs generate an analog or digital output signal indicative of the motor phase current as may be used in controlling motor position and speed.
In-line current sensing in a motor application and other applications can be complicated by relatively large common mode voltages experienced by the sense resistor and thus also by the circuitry coupled to detect the current through the sense resistor. For example, the voltage across the sense resistor can swing between ground and a high input supply voltage level. Further, because of the inductive nature of motor windings, the resistor voltage can in fact swing beyond the supply voltage range.
Various techniques are used to electrically isolate sense circuitry from sensed elements subjected to large common mode voltages. For example, in some arrangements, a multi-chip solution entails the use of multiple integrated circuits to isolate the sense circuitry from large common mode voltages.